From the dictionary:
Professional - a person who earns a living in a sport or other occupation frequently engaged in by amateurs
Amateur - a person who engages in a study, sport, or other activity for pleasure rather than for financial benefit or professional reasons
I would hope that people research the background of anyone that they might hire, and choose appropriately. Target photographers are professionals, as in that is their source of income, but it is unlikely that they would know how to properly photograph a wedding event. Different skills are needed in different areas.